Conventionally, a research and development of a robot hand apparatus mimicking a hand of a human has been made to make the robot to do various kinds of tasks.
For representing the function of a thumb among five fingers of a human, for example, two crossing axes are required, if it is assumed a palm is facing upside (see Japanese unexamined patent publication JP No. 2003-117873). Here, one of two crossing axes is an axis for rotating a thumb in a height direction, and the other of two crossing axes is an axis for rotating the thumb in a left-and-right direction.
In the conventional robot hand apparatus, however, a total of two sets, each consisting of a motor, a reduction unit, and a motor driver, are required for each axis, for actuating the finger around two crossing axes. In this case, since the number of the parts and the weight of the robot hand apparatus are increased, this becomes the defect for a humanoid-type robot restricted in a volume and an output.
Therefore, the robot hand apparatus which can actuate a finger around two crossing axes with simple mechanism has been required.